package DoublyLinkedList;

import java.util.NoSuchElementException;

public class DLQueue {

	private Node first;
	private Node last;

	public DLQueue(){
		first = null;
		last = null;
	}

	/**
	 * adds an element to the stack
	 * @param data - the element to add
	 */
	public void push(Object data){
		Node newNode = new Node();
		newNode.data = data;
		newNode.next = first;
		first = newNode;
	}

	/**
	 * returns the last element added to the stack
	 * @return an element removed, of the type Object
	 */
	public Object pop(){
		if(first == null){throw new NoSuchElementException();}
		Object temp = first.data;
		first = first.next;
		return temp;
	}

	/**
	 * returns the last element added to the stack
	 * @return an element of the type Object
	 */
	public Object peek(){
		if(first == null){throw new NoSuchElementException();}
		return first.data;
	}

	/**
	 * adds an element to the list
	 * @return
	 */
	public void add(Object data){
		  Node newNode = new Node();
		    newNode.data = data;
		    newNode.next = first;
		    newNode.previous = null;
		    if (first == null) {
		    	last = newNode;
		    	}
		    else {
		    	first.previous = newNode;
		    	}
		    first = newNode;

	}

	/**
	 * removes an element in the current position of the iterator
	 * @return - the element that is removed
	 */
	public Object remove(){
		if(first==null){
			throw new NoSuchElementException();
		}
		else if(first == last){
			last = null;
		}
		Object temp = first.data;
		first = first.next;
		return temp;
	}



	class Node{
		public Object data;
		public Node next;
		public Node previous;
	}

}